World shrimp industry has grown until the early 1990's without any threatening of severe diseases. Vibriosis was a major disease threatening the farming yield of shrimp in the late 1980s and the early 1990s. However, new deadly viruses like yellow head virus, white spot syndrome virus, Taura syndrome virus, etc. were introduced in the 1990s, which exerted a severe bad effect on shrimp farming yield.
Particularly, white spot syndrome virus of shrimp is broadly happening from Asia, including Korea and Japan, to Central and South America, and then its economic damage is very severe. White spot syndrome virus is a double-stranded DNA virus of which host is various kinds of crustaceans, and belongs to genus Whispovirus and family Nimaviridae (van Hulten M. C. W et al., J. Gen. Virol., 81, pp 307-316, 2000). Virion is relatively large (80-120 nm×250-380 nm) and has three pellicles, and its shape is rod or oval. After an arthropod like shrimp, crayfish, crab, etc. is infected with white spot syndrome virus, white spot happens on integument of shrimp like gills, mesothelium, carapace, appendage, cuticle, etc. and infected arthropod shows lethargy, reduced movement, and sudden reduction in food consumption. 3˜5 days after the infection, infected arthropod falls dead (J. M. Vlak et al., XII International Congress of Virology, Paris, 2002).
According to scientists discovering the virus and areas, the white spot syndrome virus is also called as WSSV (white spot syndrome virus), WSV (white spot virus), WSBV (white spot baculovirus), CBV (Chinese baculo-like virus, HHNBV (hypodermal and hematopoietic necrosis baculovirus), PV-PJ (rod shaped virus of Penaeus japonicus), PRDV (penaeid rod-shaped dovavirus), PAV (penaeid acute viremia), SEMBV (systemic ectodermal and mesodermal baculo-like virus) and so on. However, those viruses are identified as the same virus.
There are many studies and developments to decrease a damage of white spot syndrome virus, and most studies and developments are focused on immuno-stimulation of arthropod. Lipopolysaccharide, glucan, fucoidan and so on are conventionally used, but their effects are not enough to substantially reduce the damage of the virus. In addition, chitosan, saponin, lactoferrin, dextran, inulin, etc. are reported to have some effect (Newman S. G., Fifth Ecuadorian Aquaculture Conference, October pp 28-30, 1999).
Use of plant extract as anti-virus medicine has been tried from a long time ago, and recently effects of some plant extracts are scientifically investigated. Some plant extracts are reported to have anti-virus effect on white spot syndrome virus of shrimp. For example, Clinacanthus nutans (Direkbusarakom S., et al., Fish Pathology, 33(4), pp 410-404, 1998) and some conventional plants (Direkbusarakom S., et al., Fish Pathology, 31(4), pp 209-213, 1996) of Thailand, and Phyllanthus spp. plants (Direkbusarakom S., et al., Diseases in Asian Aquaculture II. Manila, pp 81-88, 1995) are studied. In South Korea, licorice root, Cnidium officinale, peanut, buck wheat, Codium fragile and layer are also reported to have some suppressing effect on white spot syndrome virus. However, there is a need for a composition having better treating or preventing effect on white spot syndrome virus.